Oscillograph scale system



All@ 12, 1941 R F. CLL-:AVER EAL 2,25,984

OSCILLOGRAPH SCALE SYSTEM Filed May'Zl, 1938 2 Sheets-Sheet l EEO HUE/6 Aug 12, 1941 R. F. cLEAvER ET Al.. 2,251,984

OSCILLOGRAPH SCALE SYSTEM WEA/W6 20A/5 l iii.

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OSCILLOGRAPH SCALE SYSTEM Richard Francis Gleaver, Ivor Reginald .Velin James, and Charles Frederick Allen Wagstaie, London, England, assignors to International Standard Electric Corporation, New York, N. Y.

Application May 2l, 1938, Serial No. 209,230 In Great Britain May 28, 1937 4 Claims. (Cl. 177--329) This invention relates to cathode ray apparatus Fig. 1a is a fragmentary view of a. detail of and more particularly to such apparatus in which Fig. 1;

a scale or the like is associated with the iluores- Fig. 2 is a modication of the arrangement of cent screen of a cathode ray tube for the pur- Fig. 1;

pose of giving a measurable indication. 5 Fig. 3 shows another embodiment in which a One example of the use of such apparatus is a virtual image of the scale is viewed by the obcathode ray oscillograph tube employed in conserver;

junction with a radio direction nder to give a Fig. 3a illustrates an embodiment in which a visual indication of the bearing of a distant stavirtual image of the oscillograph screen is viewed tion in the form of the angle, read oi on a suitl by the observer;

able scale, between a luminous line on the screen Fig- 4a ShOWS an arrangement for producing a of the oscillograph, due to the signal, and a xed phciicg'raphic transparency 0f a Scale;

reference line on the scale. So far as we are Fig. 4b shows a System fOr Projecting a real aware, the plan heretofore used is` to paint or vinnige 0f this photographic transparency 0n the 'print the scale on the end of the oscillograph 15 OScllOgIaDll Screen;

tube. This system suiers from numerous disad- Fg- 5 ShOWS another embodiment in which a vantages. The painting or printing of the scale Teal image 0f a Scale iS Prcjeeted Onto the 0son the curved surface at the end ofthe tube clllceaph Screen, a virtuel image 0f Which is presents considerable difficulty. The scale has VleWed;

to be illuminated and the light falling on the Fie'- 5a ShOWS a detail 0f Fig. 5; and

screen diminishes the relative brilliance of the Fig- 5b ShOW'S an arrangement for magnifyline due to the signal. Moreover, the scale is me the virtual image produced by the arrangexed relative to the deiecting plates of the osclment 0f Flg- 5- lograph. This renders it necessary tolay out the Referring t0 Flg- 1 C- R T- represents the direction nder aerials always with a predeterend of the athode ray tube and SS lille Oscilmined orientation which may be very inconlogl'eph Sel'ecn- The Scale E iS engraved 0n the vement back surface of a piece of plate glass G placed An object of the invention is the provision of in front of and almost in contact with the end a scale system for cathode ray tube oseillographs of* the tube- In this gme and in the Other inwhich these disadvantages are overcome. This gures the Seele in Secticn 01 ii'S electronic object is achieved by disasssociating the actual image is Shown es e Solid 01' e dotted arl'OW- scale from the oscmograph screen. The plate G is illuminated from the edge by a According to one feature of the invention in a tubular filament lamp s Sul'elmded by a metal cathode ray oscillograph scale system, the scale reflector R' A black mess Z Shown in Flgla, is provided on a sheet of glass or on a p1an0 35 extends over the edges of the glass plate. The concave lens which is placed in front of the osengraving Sheuld be lled With Opaque material cillograph screen and through which the screen to prevent hght from passing back onto the is viewed by the observer. Screen SS- According to another feature of the inven- In the above arrangement PeYallaXWill Occur tion a real or a virtual image of the scale is 40 ,it the regions .P pear the edges of the scaleadapted to be viewed by the observe-r on the 0s o overcome this disadvantage the sheet of glass laced by a plano-concave lens L Fi cillograph screen, or,conversely a vlrtual image may be Igp i g of the oscmograph screen may be viewed by the 2, of required diameter and curvature. 'Ihe conobserver on a scale dsassocmed wth the s .ireenlesli asi According to another arrangement e real image lograph tube C. R. T. Parallax is thus greatly of the scale is prOJeCted 0n the csellleeenh reduced because of the reduced spacing between screen and a virtual image of the screen 1s the scale and the tube surface viewed by the observer. In either of the above-described arrangements 'Ihese and other features of the invention will 50 the scale may be produced on the glass plate G or be more clearly understood from a reading of the lens L by photographic means or acid etching.

following description in commotion with the ac- Referring to the modification of Fig. 3, S is a companying drawings in which: source of light, T a metal tube painted white Fig. 1 shows oneembodiment of the inveninternally and R a white diffusive reector. The

tion; Y scale S is photographed on a sheet of glass FR in clear divisions on a black ground. FG is a reflector. FR is a red illter and FG a green illter. A virtual image I' ot the scale is produced on the screen S" at the end of the cathode ray tube. The virtual image is plane but its position can be so adjusted that parallax is negligible at any desired radius on the oscillograph screen. The colour filters are used for the purpose of suppreing the reflection of S' at the back surface of the reflector FG. Gelatine-on-glass filters may be used and it has been found to be immaterial whether the front or back surface of FG carries the gelatine coating, so far as the suppression of the second reflection is concerned.- However, a better reflection of the scale is obtained from the uncoated surface of the glass and in practice the dyed gelatine coating is placed on the back of the plate glass reflector. nearer the oscillograph. Polarisingiilters may be used in place of colour filters.

Fig. 3a shows a further modiilcation using one colour iilter FR or a thinly silvered mirror. S is a source of light, C a condenser and 0. a sheet of opal glass. The scale S' is photographed on a sheet of glass placed in front of the opal glass O. 'I'he reflector FR acts as a red lter and causes a virtual image I' of the signal image I at the end of the screen to appear on the scale S'. The colour lter FR in this case operates in a manner exactly like the filters of Figure 3. source S and the glass screen O will readily pass through filter FR and continue on to the eye and the blue green light from the cathode ray tube, or the signal image will be reflected from the color filter plate FR. There will be no double image formation of the signal image since the v red iilter material on the plate will not allow the blue green light to pass through the plate or if the color lter material were on the opposite side of the plate would not allow the blue green light to be reflected from the opposite surface of thatplate. A thinly silvered mirror which reects say 90% and transmits say 10% of incident light may be used in place of the filter FR. The use of a. thinly silvered mirror is to be preferred since it permits the use of a scale of any colour and gives a more brilliant ,image.'

According to a further modification illustrated in Fig. 4b, a real image I' of an undistorted scale is projected onto the end of the oscillograph tube C. R. T. The real image may be projected from a slide T' produced from a photograph obtained in the manner shown in Fig. 4a, in which S is a source of light, C a

condenser, T a. photographic transparency of the scale with white lines on a black ground, L a projection lens, and K a wooden model of the end of the oscillograph tube painted white. A photograph istaken of the projection I of the scale on the block, by means of a camera Ca Vdispodonalineatanangletotheaxis-.on which S, C, T, L and K are located. A real image I (Fig. 4b) of the scale on the photographic transparency T' (htained from the photograph is then projected on the end of the tube C. R. T. in a manner which will be obvious from Flg.4binwhichSisalightsource,Cacon denser and L" a projection lens. The lenses L, L' and L" (Figs. 4a and 4b) are used with small stops to give sharp focus. ner an undistorted scale can be projected onto the screen of the oscillograph from a point not The red light coming from theY Inthisxnan-Y projection lens L" (Fig. 4b) from the end of the tube C. R. 'I'. and the angie of projection t, should of course correspond respectively to the distance of the lens L' of the camera Ca (Fig. 4a) from the surface of the block K and the angle at which the photograph of the real image of T on the block K was taken.

Referring now to Fig. 5, which illustrates another embodiment very suitable for rack mounting, a real image I of a transparency of the scale T (clear markings on an opaque ground) is projected by a projector comprising light source S, condenser C and projection lens PL, onto the screen of the osclllograph tube C. R. T. Between the projector and the screen is interposed a mirror M. of special construction, having its plane at 45 to the axis of the oscillograph and thus permitting the screen to be viewed in a direction perpendicular to its axis. I' is the virtual image of 'the end of the tube. FP is the front panel of the apparatus. In order to avoid trouble due to double reflections, the mirror M must be very thin and silvered preferably on the front surface. As shown in Fig. 5a, it is formed with a number of thin circular concentric slits in its reflecting surface, which permit light from the projector to pass through the mirror without appreciably aecting the quality of the reflection of the oscillograph screen. The entire oscillograph screen is visible from any point within the shaded area indicated in Fig. 5.

A further improvement may be effected by adding a simple magnifying lens L, Fig. 5b, of large aperture through which the virtual image in the mirror M is viewed. Although this will not increase the apparent size of the image when viewed from near the front panel it will result in a considerable increase in the apparent size and hence the accuracy of observation when the oscillograph is viewed from a normal distance of say 12 inches from the front panel FP of the apparatus. Since the lens is adjusted so that the tube is at the full length XI' of the lens L it will enable accurate readings to be taken at a considerable distance from the equipment, the distance being limited only by the diameter of the magnifying lens L.

In all the above-described arrangements the North point on the scale is at the top and facilities are provided for rotating the cathode ray tube on its axis to accommodate any orientation of the direction finder serials.

What is claimed is:

1. A cathode ray tube indicator arrangement comprising a cathode ray tube having a target at one end thereof, a transparent scale carrying means arranged parallel to the axis of said tube, a source of light arranged back of said scale carrying means, and a partially reecting, partially transparent means arranged at a 45 angle with respect to said target and said scale carrying means for producing an apparent superposition of said scale and said target means of a virtual image.

2. A cathode ray tube indicator arrangement comprislngacathoderaytubehavingatarget in one end thereof, a transparent scale carrying means arranged parallel to the axis of said tube, a source of light arranged back of said scale carrying means, a reflecting means arrangedata45 anglewithrespecttosaid targetandsaidscalecarryingmeans,forpro ducing an apparent superposition of said scale and said target by means of a virtual image,

ontheaxisofthetube. 'Ihedistancedofthe'l andcolorltermeanstopreventdirectsuperposition of light from said ta-rget and said scale on either of said devices.

3. A cathode ray tube according to claim 2 in which said scale is formed on a sheet of glass and the viewing direction is such that a virtual image of said scale is seen on said target.

4. A cathode ray tube indicator arrangement comprising a cathode ray tube having a target in one end thereof, a transparent scale carrying means arranged parallel to the axis of said tube, 10

a source of light arranged back of said scale carrying means, a partially silvered mirror arranged at a. 45 angle with respect to said target and said scale carrying means, for producing an apparent superposition of said scale and said target by means of a virtual image.

RICHARD FRANCIS CLEAVER.

IVOR REGINALD JOHN JAMES.

CHARLES FREDERICK ALLEN WAGSTAFFE. 

